气吸式精量播种机常见故障的原因分析及其预防和排除方法

气吸式精量播种机是当前国内外普遍采用的精量播种机的主要类型。笔者根据多年来的体验，分析生产实践中较常见的故障原因并归纳其预防和排除方法如下。

水力压力波动注入压裂增产工艺的力学原理

为了提高水力压裂的改造增产效果,解决连续油管环空水力压裂作业中高泵压的难题,提出了一种新的水力压力波动注入压裂增产工艺。基于水力压裂原理,解释了水力压力波动注入条件下井筒压力系统变化规律;根据流体力学、弹性力学及波动力学理论,建立了水力压力波动注入压裂增产工艺的基础力学原理。分析结果表明,水力压力波动注入条件下,井筒内流动流体发生了能量转换,在井底附近产生了不稳定的压力波动,这种由于不稳定注入排量产生的不稳定的压力波动在储层裂缝内以压力波的形式传播;水力压力振动波沿缝长方向传播时并不是以恒定压力振幅传播,而是呈现压力振幅衰减的规律;水力裂缝的长度和宽度随着压裂泵工作转速的增大而增加。研究结果表明,水力压力波动注入压裂增产工艺可以提高水力压裂的改造效果和油气井的产量,建议将该工艺方法应用到现场水力压裂作业中。

Instability characteristics of the cracked roof rock beam under shallow mining conditions

To establish the movement relationship for the roof breaking under shallow mining conditions, the mechanical model of the roof rock beam was built, then the structure instability process of the roof rock beam was analyzed. The changing criterion of the vertical displacement was established and the relationship between the deflection and the rotary motion of roof block was determined. Regarding a mining face in Shangwan Mine, the responsing laws of the deflection and horizontal thrust of the roof rock beam were obtained through FLAC3D numerical analysis. The results show that the structure instability of the cracked roof rock beam depends on the interaction between the vertical load and the horizontal thrust.For the roof rock beam, when the vertical load keeps constant, the horizontal thrust fluctuating rises with increasing deflection. The horizontal thrust increases constantly with the deeper buried depth and the smaller span.

再议气吸播种机

首先表述了播种是农业生产所有环节中最重要的一环,其次对气吸式播种机排种器的工作原理加以说明。而后对气吸式播种机播种深度不稳定的影响因素、排种量不稳定的影响因素进行了深入的分析和实践的总结,最后提出了提高排种器可靠性的措施。